title: Isolation of the membrane-binding peptide of NADPH-cytochrome P-450 reductase. Characterization of the peptide and its role in the interaction of reductase with cytochrome P-450.
abstract: A peptide identified as the membrane-associated segment of NADPH-cytochrome P-450 reductase has been generated by steapsin protease treatment of vesicle-incorporated reductase and isolated by preparative gel electrophoresis. This peptide remains associated with vesicles when steapsin protease digests of vesicle-incorporated reductase were fractionated by Sepharose 4B chromatography, confirming its identity as the membrane-binding peptide. The molecular weight of the membrane-binding peptide was 6400 as determined by gel filtration in 8 M guanidine hydrochloride, and its amino acid content was not especially hydrophobic. The activity of reconstituted hydroxylation systems consisting of reductase, cytochrome P-446, and dilauroyl phosphatidylcholine was not inhibited by large molar excesses of purified membrane-binding peptide. Moreover, when purified reductase and cytochrome P-446 were added to liposomes which contained the membrane-binding peptide, it was determined that mixed function oxidase activity was reconstituted as effectively as when vesicles without the membrane-binding peptides were used. Similar results were obtained with reductase, cytochrome P-450, and detergent-solubilized liposomes (with or without the membrane-binding peptide). Thus, the membrane-binding peptide does not appear to interact with either of these two forms of the hemoprotein in a site-specific manner to prevent reconstitution of hydroxylation activity.
mesh_terms: D015660:7-Alkoxycoumarin O-Dealkylase; D000596:Amino Acids / Q000032:analysis; D000818:Animals; D001665:Binding Sites; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D046911:Macromolecular Substances; D008565:Membrane Proteins / Q000302:isolation & purification* / Q000378:metabolism; D006899:Mixed Function Oxygenases / Q000378:metabolism; D009251:NADPH-Ferrihemoprotein Reductase / Q000302:isolation & purification* / Q000378:metabolism; D010089:Oxidoreductases, N-Demethylating / Q000378:metabolism; D010105:Oxygenases / Q000378:metabolism; D010455:Peptides / Q000302:isolation & purification* / Q000378:metabolism; D011485:Protein Binding
chemical_list: D000596:Amino Acids; D046911:Macromolecular Substances; D008565:Membrane Proteins; D010455:Peptides; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; D010105:Oxygenases; D015660:7-Alkoxycoumarin O-Dealkylase; C019781:benzphetamine N-demethylase; D010089:Oxidoreductases, N-Demethylating; D009251:NADPH-Ferrihemoprotein Reductase